Device for vaporization of volatile anesthetic liquids



Dec. 7, 1965 I I J. A. FELTS 3,221,737

DEVICE FOR VAPOBIZATION 0F VOLA'IILE ARESI'HE'I'IO LIQUIDS Filed July25, 196? 2 Sheets-Sheet 1 PRESSUR E FRO" FLOW" E YER Dec. 7, 1965 J. A.FEL'I'S 3,221,737

DEVICE FOR VAPORIZATIOII OP VOLATILB MIES'I'HETIO LIQUIDS F1106 July 25.1962 2 ShOOMhIOl B INVENTOR JAMES A. FEU'S ATTORNEYS United StatesPatent Ofifice 3,221,737 DEVICE FOR VAPORIZATION F VOLATILE ANESTHETICLIQUIDS James A. Felts, 517 Bainbridge Road, Marion, Ill. Filed July 25,1962, Set. No. 212,409 Claims. (Cl. 128-188) This application is acontinuation-in-part of my application entitled Device for vaporizationof Volatile Anesthetic Liquids, Serial Number 82,043, filed January 11,1961, now Patent No. 3,123,071.

This invention relates to an anesthetic vaporizing assembly which isdesigned to give a patient a constant percent concentration of a desiredanesthetic. It is particularly well adapted for use in an absorptiontype closed circuit anesthesia system, but it may also be efiicientlyutilized in other environments.

It is an object of this invention to provide a means of automaticallymetering a liquid anesthetic into an anesthesia circuit at a rate whichis dependent upon the volume of metabolic oxygen or other gases injectedinto the patients breathing circuit.

Another object is to provide an easily operated, reliable, and etiicientmeans of metering an anesthetic to apatient receiving anesthesia from aclosed circuit absorption type system.

A further object is to provide an anesthetic metering device which iscapable of continuously producing a selected percent of anesthetic vaporin any desired volume of gas being led to the patient's breathingcircuit.

Another object is to provide an anesthetic metering and vaporizingassembly which is so designed that it prevents extreme variations in thetemperature of the assembly and thus prevents excessive fluctuations inth percent of anesthetic vapor'delivered.

A closed circuit anesthesia system is one in which the patients facemask has two conduits leading therefrom. One of these receives the airexhaled by the patient and the other supplies air to the patient uponinhalation. Suitable check valves in the face mask cause the flow asdescribed.

The inhalation conduit and exhalation conduit are joined at some remotepoint and form a circuit which is closed to the outside atmosphere. Flowthrough the circult is caused by the breathing of the patient; Carbondioxide and other impurities are removed by suitable means, andmetabolic oxygen or other-gases are added to supply the needs of thepatient. Likewise, an anesthetic is injected into the circuit.

An improved vaporizer for such a system wherein a liquid anesthetic istransformed into its gaseous state is the subject of my c0-pendingapplication, Serial Number 82,043, filed January 11, 1961, and entitledDevice for vaporization of Volatile Anesthetic Liquids," Patent No.3,123,071. The instant invention is particularly well adapted for usewith my vaporizer, but may find equally satisfactory applications withother closed circuit anesthetic vaporizer-s. i

As mentioned above, metabolic oxygen or other gases are added to theclosed circuit anesthesia system. In the preferred embodiment of thisinvention, the influence of these gases to the system would provide theforce which meters the liquid anesthetic into the'vaporizing chamberdescribed in my above mentioned co-pending application. Using the novelsystem described hereafter, the amount of liquid anesthetic metered intothe system will be dependent upon the amount of external gases added tothe circuit and will maintain a constant percentage thereof.

My invention may best be understood by reference to the accompanyingdrawings wherein:

FIG. 1 is a view partially in section, of the improved metering devicemounted on a vaporizing chamber; and

3,221,737 Patented Dec. 7, 1965 FIG. 2 is a view taken along line 2-2 inFIG. 1 and showing the general configuration of the vaporizer as semblyincluding the metering portion and the vuporiz ing portion; and

FIG. 3 is a view taken along line 3-3 in FIG. 1 of a dial and scale usedfor adjusting the anesthetic flow into the vaporizer chamber.

In the prior art, anesthetics have sometimes been manually inject-edinto the flow circuit of a closed circuit system by a syringe-likedevice. My invention provides a means to eliminate this tedious andinaccurate means of V injecting the liquid anesthetic and to produce asystem which will automatically vary the amount of anesthetic vaporizedas the flow of gases added to the system is varied.

Another prior art device is the "blow-over" system in which a. meteredamount of gas is passed over a reservoir of liquid anesthetic. Thisdevice is calibrated to deliver a given percent of vapor. Still anothersystem allows a metered amount of gas to bubble through a reservoir ofanesthetic liquid. This gives a stated percent concentration which isdependent upon the temperature and vapor pressure.

In order to deliver a certain percent of vapor to the patient, theblow-over" and bubble systems require a specific flow of gas. Since thegas required by a patient varies from case to case, it is obvious thatsome of the gas and anesthetic vapor must be bled oil? before arrivingin the patients breathing circuit. This is a breach of the air-tightintegrity of the system and also results in unnecessary waste of the gasand anesthetic.

Both of these latter mentioned prior art systems vaporize the anestheticon or within the surface of the reseryou: or liquid anesthetic. Thisvaporization lowers the temperature of the liquid in the reservoir, thuschanging the vapor pressure of the liquid anesthetic which, of course,varies the percent concentration of vapor which passes to the patient.

In my improved apparatus there is no need for supplying an excessiveamount of gas in order to achieve a desired percent vapor concentration.Also, the vaporization of'the anesthetic takes place in an area removedfrom the liquid reservoir, thus eliminating any variations due totemperature changes of the liquid anesthetic. Furthermore, the efiicientdesign of my vaporizing chamber with its improved thermal efliciency andabundant surface area eliminates substantial temperature variations.This is more fully discussed in my above-identified co-pendingapplication.

Referring to FIG. I, a metering device generally designated 2 is securedatop a vaporizing chamber 4 which is in communication with the patient'sbreathing circuit, shown passing through a passage 12 having an inletconnection 6 and an outlet connection 8.

As described in my co-pending application, the gases flowing through thepassage 12 in the base 14 of the vaporizing chamber 4 cause a reducedpressure at the throat of a venturi 16. Passage 17 connects this zone ofreduced pressure with the vaporizing chamber. Likewise, a passage 18leads from an enlarged portion 20 of the passage 12 to the vaporizingchamber 4. The pressure dilference between passages 17 and 18 causessome of the gas flowing through passage 12 to be diverted through thevaporizing chamber. These gases are drawn into the vaporizing chamberthrough passage 17; whereafter they mix with vaporized anesthetic andthen pass from the vaporizing chamber through passage 18 back intopassage 12. The vaporizing chamber 4 may therefore. be considered aportion of the breathing circuit, since some of the gases in the circuitare regularly circulated therethrough.

The liquid anesthetic is metered onto the hemispherical dome 21 in thevaporizing chamber by the metering device 2.

Before use, a liquid anesthetic is placed in a reservoir 22 in themetering device by removing the cap 24 and pouring it into a funnelopening 28. A drain cook is located at the lowermost point of thereservoir to facilitate cleaning and drainage.

The liquid anesthetic may flow through a small orifice 32 in the bottomof reservoir 22 into a pressure chamber 34. It is from this pressurechamber that the liquid anesthetic is forced into the vaporized chamber4.

The anesthetic is maintained at a constant depth in the pressure chamberby a float valve assembly.

A float 38 is supported by arms 39 which are hinged by pins 40 to a lugon an upstanding sleeve 59 closed at its top. The float is free to riseand fall as the liquid depth varies. The free end of float 38 supportsthe shank of a needle valve 42 which seats in the orifice 32. Needlevalve 42 has an enlargement 43 thereon to prevent it from fallingthrough its supporting member 45. An aperture 47 allows the liquid toflow from within member 45 to the pressure chamber 34. A vent tube 49passes from pressure chamber 34 to a point in reservoir 22 above theliquid level therein. This facilitates the flow of liquid anestheticthrough aperture 32 by equalizing the pressure. It can be seen that asthe liquid anesthetic u'n chamber 4 is depleted, the needle valve willopen and restore the fluid to the desired level. The needle valve willclose aperture 32 when the liquid reaches such level. Pressure chamber34 also has a drain cock, located at 44.

Air or gas is delivered to the pressure chamber 34 through an inlet 46.In the preferred arrangement, the pressure source is from the fiowmetersof a standard anesthetic machine. Metabolic oxygen or oxygen and othergases are thus supplied to the closed circuit system. These flowmetersprovide gases at a constant volumetric rate of flow.

Vent ducts, 48, 50 and 52 communicate between the pressure chamber 34and the vaporizing chamber 4, allowing the oxygen or other gases to passinto the breathing circuit. A regulating valve 54 is located in the vent48 and may partially impede the flow of gases therethrough, and thus mayregulate the pressure within the pressure chamber 34. Regulating valve54 is preferably a needle valve with a threaded shank and it is providedwith an adjusting knob 60.

The liquid anesthetic passes from pressure chamber 34 to the vaporizingchamber 4 through a fluid passage or tube 58. One end of tube 58 islocated beneath the surface of the liquid anesthetic and the other anddischarges into a sleeve 59 closed at its upper end, directly above thedome inside the vaporizing chamber. The tube passes above the liquidlevel of the anesthetic in chamber 34, so there is no gravity flow ofthe fluid.

The pressure is chamber 34 is normally maintained at a higher level thanthat in vaporizing chamber 4. This naturally results in a flow of theliquid anesthetic through tube 58 to the vaporizing chamber.

A most significant feature of the instant invention is the use of theregulating valve 54 to control the amount of anesthetic which isdispensed. Since the amount of liquid anesthetic dispensed relies whollyupon the pressure ditferential between chambers 34 and 4 and since thevalve 54 is located in a vent duct between these two chambers, anyadjustment of the valve will result in a change in the pressuredifferential. Opening valve 54 fully would equalize these pressures andno fluid would flow. Similarly, by closing the valve 54 the maximumamount of anesthetic would flow.

The amount of metabolic oxygen or other gases required by a patient willvary from case to case. Sometimes the flow for small children will be aslow as 50 cc. per minute.

Within the range of gas flow required for the closed circuit typeanesthetic system, it has been found that for any setting of theregulating valve 54, the amount of anesthetic metered into thevaporizing chamber is directly proportional to the volume of gases beingintroduced through gas inlet 46. With a given valve setting, a change inthe gas admitted through inlet 46 does not vary the percent of vapordelivered into the breathing circuit from the vaporizing chamber. Thisis because the amount of liquid delivered through tube 58 will chage inproportion to the change in gas flow.

With any given gas flow, the percent of vapor may readily be changed byadjusting the regulating valve 54, which will result in the admission ofmore or less liquid anesthetic into vaporizing chamber 4 into a constantvolume of gas.

To enable the operator of the device to ascertain the ratio of liquidanesthetic to gas, the knob 60 of the regulating valve 54 may beimprinted with a pointer as shown at 62, see FIG. 3. The scale 56 isgraduated in percentage of any desired anesthetic vapor, some of whichare shown on the scale illustrated in FIG. 3.

In a metering device of this nature, it is important that the properdosage is given to a patient, or severe physical harm may result. Toprevent the knob 60 on the regulating valve from receiving more or lessturns than desired, the knob is provided with a projection 64 on itsedge which, when the pointer 62 is at its furthest position to theright, will abut against a stop 66 to prevent furthcr rotation.

In operation, the improved metering device is first filled with thedesired anesthetic. The regulating valve knob is adjusted to the percentdosage which is needed for the particular patient and case. Then thefiowmeters are adjusted to provide the required flow of gases throughthe gas inlet 46.

As described above, the pressure in the pressure chamber 34 willincrease as the regulating valve 54 is closed, and a greater flow ofliquid anesthetic will result. When the regulating valve is kept at anygiven setting, and the flow of gases admitted through gas inlet 45 isincreased, the pressure in chamber 34 will increase and acorrespondingly increased flow of liquid anesthetic into vaporizingchamber 4 will ensue, resulting in the same percent of vapor beingdelivered from the device.

From the above description, one may readily see that my improvedmetering device overcomes many of the shortcomings of the prior art.First, it makes it possible to meter an anesthetic into small amounts ofgas and eliminate the necessity of bleeding anesthetic vapor and gasfrom the system. This makes this device especially useful inadministering an anesthetics to children and to certain other patientsrequiring small amounts of gas.

Another notable improvement is that the percent of vapor delivered inthe gas stream may be easily varied by changing the regulating valvesetting, and the percent will remain constant, regardless of the rate ofgas flow to the patient.

It is understood that many modifications may become apparent and thescope of thisinvention is not limited only to the above-describedembodiment but by the claims which are appended hereto.

I claim:

1. An anesthetic vaporizer assembly for use in a closed circuitanesthesia system comprising a vaporizing portion and an anestheticmetering portion, said vaporizing por tion having a vaporizing chamberformed by a housing with a central tower therein, said vaporizingchamber having an inlet conduit and an outlet conduit, a breathing lineconnected to each or said conduits, venturi means in said breathing lineto create a pressure diiferential between said inlet and outlet conduitsto create a gas flow through said vaporizing chamber; said anestheticmetering portion having a pressure chamber partially filled with liquidanesthetic, means to supply gas at a constant rate of flow to saidpressure chamber, means regulating the pressure in said pressure chamberincluding a gas duct passing from said pressure chamber to saidvaporizing chamber, said gas duct having a variable obstruction therein,a fluid conduit passing from a portion of said pressure chambersubmerged by-liquid anesthetic to said vaporizing chamber.

2. In combination, a breathing circuit and a metering device for liquidanesthetics, said metering device having a pressure chamber partiallyfilled with a liquid anesthetic, means for supplying gas at a constantrate of flow to said pressure chamber, means for regulating the pressurein said chamber including a gas duct with an adjustable obstructiontherein passing from said pressure chamber to said breathing circuit, afluid passage leading from a portion of said pressure chamber submergedby liquid anesthetic to said breathing circuit.

3. In combination, a breathing circuit and a metering device for liquidanesthetics, said metering device having a pressure chamber partiallyfilled with a liquid anesthetic,

means for supplying gas at aconstant rate of flow to said pressurechamber, means for regulating the pressure in said chamber including agas duct leading from said pressure chamber to said breathing circuit, aneedle valve positioned in said duct, and a fluid passage leading from aportion of'said pressure chamber submerged by liquid anesthetic to saidbreathing circuit.

4. In combination, a breathing circuit and a metering device for liquidanesthetics, said metering device having a pressure chamber partiallyfilled with a liquid anesthetic, a fluid passage leading from a portionof said pressure chamber submerged by liquid anesthetic to saidbreathing circuit, means for supplying gas at a constant rate of flow tosaid pressure chamber, means for regulating the pressure in saidpressure chamber including a gas duct leading from said pressure chamberto said breathing circuit, a needle valve positioned in said duct, meansfor indicating the position of said needle valve, a scale associatedwith said indicating means, said scale graduated in ratios of anestheticto gas.

5. In a device for metering liquid anesthetics into a breathing circuit,a reservoir chamber for a liquid anesthetic, a pressure chamberpartially filled with ,liquid anesthetic, a breathing circuit, anorifice between said reservoir chamber and said pressure chamberallowing gravity flow of liquid anesthetic therethrough, a float intheliquid in said pressure chamber, means associated with said float toobstruct said orifice when a desired liquid level is attained in saidpressure chamber, means supplying gas at a constant rate of flow to saidpressure chamber, means for regulating the pressure in said pressurechamber including a gas duct with an adjustable obstruction.

therein passing from said pressure chamber to said breathing circuit, afluid passage leading from a portion of said 6 pressure chambersubmerged by liquid anesthetic to said breathing circuit.

6. A system for administering a vaporized liquid anesthetic comprising,in combination, a breathing circuit leading to a patient, said circuitincluding an anesthetic vaporizing area, and a metering device fordispensing a liquid anesthetic into said vaporizing area; said meteringdevice having a pressure chamber with a liquid level therein,

area of said breathing circuit.

9. The system of claim 6 wherein said venting means is a duct having aneedle valve therein, said needle valve having means indicating theposition thereof, a scale graduated in ratios of anesthctic-to-gasassociated with said indicating means.

10. An anesthetic vaporizer assembly comprising a vaporizing chamber andan anesthetic metering portion, said anesthetic metering portion havinga pressure chamber partially filled to a liquid level with liquidanesthetic, means for supplying gas at a constant rate of flow to saidpressure chamber, means regulating the pressure in said pressurechnmber'including a gas duct passing from said pressure chamber to saidvaporizing chamber, a variable obstruction in said gas duct, a fluidconduit passing from a portion of said pressure chamber below saidliquid level to' said vaporizing chamber, and means adapted to connectsaid vaporizing chamber to a patient's breathing line.

References Cited by the Examiner UNITED STATES .PATENTS 1,738,75712/1929 Bragdon 239--347 2,141,794 12/1938 King l28-188 2,243,435 5/1941 Mott et al 239-347 3,018,777 1/ 1962 Dietrich 128l88 3,021,8402/1962 Hallamore et a1 128-183 I FOREIGN PATENTS 6,312 3/ 1903 GreatBritain. 519,203 3/ 1940 Great Britain.

OTHER REFERENCES V. Mueller & COL, Catalog No. 65, Chicago, Ill., 1963(p. 745 relied on).

RICHARD A. GAUDET, Primary Examiner. JORDAN FRANKLIN, Examiner.

2. IN COMBINATION, A BREATHING CIRCUIT AND A METERING DEVICE FOR LIQUIDANESTHETICS, SAID METERING DEVICE HAVING A PRESSURE CHAMBER PARTIALLYFILLED WITH A LIQUID ANESTHETIC, MEANS FOR SUPPLYING GAS AT A CONSTANTRATE OF FLOW TO SAID PRESSURE CHAMBER, MEANS FOR REGUALTING THE PRESSUREIN SAID CHAMBER INCLUDING A GAS DUCT WITH AN ADJUSTABLE OBSTRUCTIONTHEREIN PASSING FROM SAID PRESSURE CHAMBER TO SAID BREATHING CIRCUIT, AFLUID PASSAGE LEADING FROM A PORTION OF SAID PRESSURE CHAMBER SUBMERGEDBY LIQUID ANESTHETIC TO SAID BREATHING CIRCUIT.